Pakasuchus: An Ancient Crocodile and Mammal Wannabe

Pakasuchus lived during the Cretaceous period in the Southern Hemisphere, where small crocodiles were fulfilling the same roles that small mammals. And they did so using similar body shapes and adaptations. Credit: Mark Witton

Pakasuchus was a crocodile that was "trying to be a mammal". It had a slender frame, long legs, a short skull and a variety of teeth for cutting and grinding its food. And it was only the size of a housecat. Credit: Zina Deretsky

Patrick O'Connor stares at white fragments of exposed bone. These bones are actually part of the most complete specimen of Pakasuchus kapilimai, which O'Connor would later free from the rock. Credit: J.P. Cavigelli

The skull of Pakasuchus, encased in its original red sandstone. As you can see, the animal’s mouth was tightly shut when it died, so O’Connor used a medical scanner to study the details of its unusual jaws and teeth. Credit: John Sattler

Modern crocodiles all attack by snapping at their prey with a powerful bite, as this saltwater crocodile demonstrates. The victims (or dismembered parts of the victims) are swallowing whole, without any chewing. Pakasuchus's diverse teeth and short jaws suggest that it ate its prey in a very different way. Credit: me, taken in Kakadu National Park, Australia

A specimen of Pakasuchus lies embedded in sandstone. It's only partially exposed and you can't see the skull. The animal's backbone runs from the bottom-left of the block to the top-right, where you can see its hips and two legs coming off it. The tail runs from the top-right across the top of the block. The twin rows of plates are called osteoderms - bony pieces of armour. Virtually all crocodiles have osteoderms all over their body but in Pakasuchus, they're only found in the tail. Credit: Patrick M. O'Connor